Communication voltage conversion circuit, communication device and communication voltage identification method

Abstract

The embodiment of the present invention relates to the field of wireless communication technology, and discloses a communication voltage conversion circuit, a communication device, and a communication voltage identification method. The circuit includes a receiving signal conversion circuit; the receiving signal conversion circuit includes: an input end of a first switch circuit connected to a first control end of a first communication unit, a control end connected to a first power supply, and an output end connected to a first end of a first pull-up circuit; an input end of a second switch circuit connected to a first control end, a control end connected to a second power supply, and an output end connected to the first end of the first pull-up circuit; an input end of a third switch circuit connected to the first power supply, a control end connected to a signal transmitting end of the first communication unit, and an output end connected to a signal receiving end of the second communication unit; and a second end of the first pull-up circuit connected to the signal receiving end of the second communication unit. In the above manner, the embodiment of the present invention realizes communication voltage conversion.

Description

Technical Field

[0001] Embodiments of the present invention relate to the field of wireless communication technology, and more particularly to a communication voltage conversion circuit, a communication device, and a communication voltage identification method. Background Art

[0002] With the rapid development of the Internet of Things (IoT), the intelligentization of home appliances has become a future trend in home appliance development. Various wireless communication technologies are widely used in the development and design of home appliances. Some home appliance main controllers (MCUs) use 8-bit MCUs, while others use 32-bit MCUs. 8-bit MCUs are all powered by a 5V supply voltage, and their serial communication levels are also 5V. 32-bit MCUs are powered by a 3.3V supply voltage, and their serial communication levels are naturally 3.3V. Wireless communication MCUs are all 32-bit and powered by a 3.3V supply voltage, and their serial communication levels are naturally 3.3V.

[0003] Before a wireless communication MCU can communicate with the MCU in a home appliance controller, the operating voltage of the home appliance controller MCU must be known in advance. The communication circuit conversion circuit can then be designed based on the specific operating voltage. This means that when home appliances with different operating voltages communicate, a communication voltage conversion circuit specifically designed for the appliance voltage is required, which increases the design cost of the communication voltage conversion circuit. Summary of the Invention

[0004] In view of the above problems, embodiments of the present invention provide a communication voltage conversion circuit, a communication device, and a communication voltage identification method, which are used to solve the problem of high design cost of MCU communication circuits in the prior art.

[0005] According to one aspect of an embodiment of the present invention, a communication voltage conversion circuit is provided, the circuit including a receiving signal conversion circuit; the receiving signal conversion circuit is configured to convert a voltage signal sent by a first communication unit into a communication voltage of a second communication unit; the receiving signal conversion circuit includes: a first switch circuit, a second switch circuit, a third switch circuit, and a first pull-up circuit;

[0006] The input end of the first switch circuit is connected to the first control end of the first communication unit, the control end of the first switch circuit is connected to a first power source, and the output end of the first switch circuit is connected to the first end of the first pull-up circuit; the first voltage of the first power source is the same as the communication voltage of the first communication unit; the first switch circuit is turned on or off according to a first control signal sent by the first control end of the first communication unit; when the first switch circuit is turned on, the voltage of the output end of the first switch circuit is the first voltage;

[0007] An input end of the second switch circuit is connected to the first control end of the first communication unit, a control end of the second switch circuit is connected to a second power supply, and an output end of the second switch circuit is connected to the first end of the first pull-up circuit; a second voltage of the second power supply is the same as a communication voltage of the second communication unit, and the second switch circuit is turned on or off according to the first control signal; when the second switch circuit is turned on, a voltage at the output end of the second switch circuit is the second voltage;

[0008] The input end of the third switch circuit is connected to the first power supply, the control end of the third switch circuit is connected to the signal sending end of the first communication unit, and the output end of the third switch circuit is connected to the signal receiving end of the second communication unit; the third switch circuit is turned on or off according to the voltage signal sent by the signal sending end of the first communication unit; when the third switch circuit is turned on, the output end of the third switch circuit outputs the voltage signal sent by the signal sending end of the first communication unit;

[0009] A first end of the first pull-up circuit is connected to the output end of the first switch circuit and the output end of the second switch circuit respectively, and a second end of the first pull-up circuit is connected to the signal receiving end of the second communication unit;

[0010] When the communication voltage of the first communication unit is different from the communication voltage of the second communication unit, the first control signal is at a high level, the first switch circuit is turned off, the second switch circuit is turned on, and the voltage at the first end of the first pull-up circuit is the second voltage; when the signal sending end of the first communication unit sends a high voltage signal to the second communication unit, the third switch circuit is turned off, and the voltage signal received by the second communication unit is the second voltage; when the signal sending end of the first communication unit sends a low voltage signal to the second communication unit, the third switch circuit is turned on, and the voltage signal received by the second communication unit is a low voltage.

[0011] In an optional manner, the first switch circuit includes: a first voltage-dividing resistor, a second voltage-dividing resistor and a first PNP transistor;

[0012] The first voltage-dividing resistor and the second voltage-dividing resistor are connected in series between the first control terminal of the first communication unit and the first power supply, the other end of the first voltage-dividing resistor is connected to the first control terminal of the first communication unit, and the other end of the second voltage-dividing resistor is connected to the first power supply;

[0013] The base of the first PNP transistor is connected to the common end of the first voltage-dividing resistor and the second voltage-dividing resistor, the emitter of the first PNP transistor is connected to the first power supply, the base of the first PNP transistor is connected to the common end of the first voltage-dividing resistor and the second voltage-dividing resistor, and the collector of the first PNP transistor is connected to the first end of the first pull-up circuit;

[0014] When the first control signal is at a high level, the first PNP transistor is turned off; when the first control signal is at a low level, the second voltage-dividing resistor and the first voltage-dividing resistor divide the first voltage, so that the first PNP transistor is turned on, and the voltage of the collector of the first PNP transistor is the first voltage.

[0015] In an optional manner, the second switch circuit includes: a third voltage-dividing resistor, a fourth voltage-dividing resistor, a first NPN transistor, a second PNP transistor and a first current-limiting resistor;

[0016] The third voltage-dividing resistor and the fourth voltage-dividing resistor are connected in series between the second power supply and the collector of the first NPN transistor, the other end of the third voltage-dividing resistor is connected to the second power supply, and the other end of the fourth voltage-dividing resistor is connected to the collector of the first NPN transistor;

[0017] The base of the first NPN transistor is connected to the first control terminal of the first communication unit through the first current limiting resistor, the collector of the first NPN transistor is connected to one end of the fourth voltage dividing resistor, and the emitter of the first NPN transistor is grounded;

[0018] The base of the second PNP transistor is connected to the common end of the third voltage-dividing resistor and the fourth voltage-dividing resistor, the emitter of the second PNP transistor is connected to the second power supply, and the collector of the second PNP transistor is connected to the first end of the first pull-up circuit;

[0019] When the first control end of the first communication unit outputs a high level, the first NPN transistor is turned on, and the collector of the first NPN transistor outputs a low level, so that the second PNP transistor is turned on, and the voltage of the collector of the second PNP transistor is the second voltage; when the first control end of the first communication unit outputs a low level, both the first NPN transistor and the second PNP transistor are turned off.

[0020] In an optional manner, the third switching circuit includes: a second NPN transistor and a second current-limiting resistor; the base of the second NPN transistor is connected to the first power supply through the second current-limiting resistor, the emitter of the second NPN transistor is connected to the signal transmitting end of the first communication unit, and the collector of the second NPN transistor is connected to the signal receiving end of the second communication unit;

[0021] When the first control end of the first communication unit outputs a high level, the second NPN transistor is turned off; when the first control end of the first communication unit outputs a low level, the second NPN transistor is turned on, and the collector of the second NPN transistor outputs a low level.

[0022] In an optional manner, the circuit further includes a sending signal conversion circuit, the sending signal conversion circuit being configured to convert the voltage signal sent by the second communication unit into a communication voltage of the first communication unit; the sending signal conversion circuit includes a fourth switch circuit, a fifth switch circuit, a sixth switch circuit, and a second pull-up circuit;

[0023] An input end of the fourth switch circuit is connected to the second control end of the first communication unit, a control end of the fourth switch circuit is connected to the first power supply, and an output end of the fourth switch circuit is connected to the first end of the second pull-up circuit; the fourth switch circuit is turned on or off according to a second control signal sent by the second control end of the first communication unit; when the fourth switch circuit is turned on, a voltage at the output end of the fourth switch circuit is the first voltage;

[0024] An input end of the fifth switch circuit is connected to the second control end of the first communication unit, a control end of the fifth switch circuit is connected to the first power supply, an output end of the fifth switch circuit is connected to the first end of the second pull-up circuit, and the fifth switch circuit is turned on or off according to the second control signal; when the fifth switch circuit is turned on, a voltage at the output end of the fifth switch circuit is the first voltage;

[0025] The input end of the sixth switch circuit is connected to the second power supply, the control end of the sixth switch circuit is connected to the signal sending end of the second communication unit, and the output end of the sixth switch circuit is connected to the signal receiving end of the first communication unit; the sixth switch circuit is turned on or off according to the voltage signal sent by the signal sending end of the second communication unit; when the sixth switch circuit is turned on, the output end of the sixth switch circuit outputs the voltage signal sent by the signal sending end of the second communication unit;

[0026] The first end of the second pull-up circuit is connected to the output end of the fourth switch circuit and the output end of the fifth switch circuit respectively, and the second end of the second pull-up circuit is connected to the signal receiving end of the first communication unit;

[0027] When the communication voltage of the first communication unit is different from the communication voltage of the second communication unit, the second control signal is at a high level, the fourth switch circuit is turned off, the fifth switch circuit is turned on, and the voltage at the first end of the second pull-up circuit is the first voltage; when the signal sending end of the second communication unit sends a high voltage signal to the first communication unit, the sixth switch circuit is turned off, and the voltage signal received by the first communication unit is the first voltage; when the signal sending end of the second communication unit sends a low voltage signal to the first communication unit, the sixth switch circuit is turned on, and the voltage signal received by the first communication unit is a low voltage.

[0028] In an optional manner, the circuit further includes a sending signal conversion circuit, which is used to convert the voltage signal sent by the second communication unit into a communication voltage of the first communication unit; the sending signal conversion circuit includes: a fifth voltage dividing resistor, a sixth voltage dividing resistor, a third NPN transistor and a second current limiting resistor;

[0029] The fifth voltage-dividing resistor and the sixth voltage-dividing resistor are connected in series between the signal transmitting end of the second communication unit and the collector of the third NPN-type transistor, the other end of the fifth voltage-dividing resistor is connected to the signal transmitting end of the second communication unit, the sixth voltage-dividing resistor is connected to the collector of the third NPN-type transistor, the emitter of the third NPN-type transistor is grounded, and the base of the third NPN-type transistor is connected to the second control port of the first communication unit via the second current-limiting resistor; the third NPN-type transistor is turned on or off according to the second control signal sent by the second control port of the first communication unit;

[0030] When the communication voltage of the first communication unit is lower than the communication voltage of the second communication unit, the second control signal is at a high level, the third NPN transistor is turned on, the sixth voltage-dividing resistor and the fifth voltage-dividing resistor divide the voltage signal sent by the second communication unit to obtain the voltage signal of the first communication unit, and send it to the signal receiving end of the first communication unit;

[0031] When the communication voltage of the first communication unit is the same as the communication voltage of the second communication unit, the second control signal is at a low level, the third NPN transistor is turned off, and the second communication unit sends a voltage signal to the first communication unit through the fifth voltage-dividing resistor.

[0032] In an optional manner, the sending signal conversion circuit also includes a protection diode; the positive electrode of the protection diode is connected to the common end of the fifth voltage-dividing resistor and the sixth voltage-dividing resistor, and the negative electrode of the protection diode is connected to the first power supply; when the voltage of the sixth voltage-dividing resistor is greater than the first voltage, the protection diode is turned on, so that the voltage at the signal receiving end of the first communication unit is less than the sum of the first voltage and the voltage drop of the protection diode.

[0033] According to another aspect of an embodiment of the present invention, a communication device is provided, which includes: a first communication unit and a communication voltage conversion circuit; the first communication unit includes a first control end, a second control end, a signal sending end and a signal receiving end; the communication voltage conversion circuit is the communication voltage conversion circuit in any of the above embodiments.

[0034] According to another aspect of an embodiment of the present invention, a method for identifying a communication voltage is provided, which is applied to a first communication unit, and is characterized in that the method includes:

[0035] Sending a low-level first control signal and a low-level second control signal to the receiving signal conversion circuit and the transmitting signal conversion circuit respectively, and sending test data to the second communication unit to obtain a test result;

[0036] If the response data sent by the second communication unit is received, determining that the test result is that the communication voltage of the second communication unit is the same as the communication voltage of the first communication unit; otherwise, determining that the test result is that the communication voltage of the second communication unit is different from the communication voltage of the first communication unit;

[0037] sending a first control signal and a second control signal to the receiving signal conversion circuit and the transmitting signal conversion circuit respectively according to the test result;

[0038] The receiving signal conversion circuit is the receiving signal conversion circuit in the communication voltage conversion circuit of any of the above embodiments; the sending signal conversion circuit is the sending signal conversion circuit in the communication voltage conversion circuit of any of the above embodiments.

[0039] According to another aspect of an embodiment of the present invention, a communication unit is provided, comprising: a processor, a memory, a communication interface, and a communication bus, wherein the processor, the memory, and the communication interface communicate with each other via the communication bus;

[0040] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute an operation corresponding to the above-mentioned communication voltage identification method.

[0041] Through the embodiment of the present invention, no matter what the communication voltage of the second communication unit MCU-B is, the second communication unit MCU-B can receive a voltage that matches its communication voltage. Compared with the prior art in which corresponding communication voltage conversion circuits are specially designed for second communication units MCU-B with different communication voltages, the embodiment of the present invention can be applicable to second communication units MCU-B with any communication voltage, thereby saving the design cost of the communication voltage conversion circuit.

[0042] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0044] Figure 1 A functional block diagram of a communication voltage conversion circuit provided by an embodiment of the present invention is shown;

[0045] Figure 2 A schematic diagram of a communication voltage conversion circuit provided by an embodiment of the present invention is shown;

[0046] Figure 3 A functional block diagram of a communication voltage conversion circuit provided by another embodiment of the present invention is shown;

[0047] Figure 4 A schematic diagram of a communication voltage conversion circuit provided by another embodiment of the present invention is shown;

[0048] Figure 5 A schematic diagram of a communication voltage conversion circuit provided by another embodiment of the present invention is shown;

[0049] Figure 6 A schematic structural diagram of a communication device provided by an embodiment of the present invention is shown;

[0050] Figure 7 A flow chart showing a method for identifying a communication voltage provided by an embodiment of the present invention is shown;

[0051] Figure 8 A structural diagram of a communication unit provided by an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0052] The following embodiments of the technical solution of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only examples and are not intended to limit the scope of protection of the present invention.

[0053] An application scenario for embodiments of the present invention is voltage conversion in wireless communications. When two communication units are communicating, if the communication voltages are inconsistent, one communication unit cannot recognize the signal sent by the other, resulting in communication failure. For example, the communication voltage of the first communication unit is 3.3V, and the communication voltage of the second communication unit is 5V. When the first communication unit sends a voltage signal to the second communication unit, the high-level signal in the voltage signal is 3.3V, and the low-level signal is 0V. The communication voltage of the second communication unit is 5V. That is, the second communication unit will only recognize the received voltage signal as a high-level signal if it receives a voltage of 5V. For a voltage signal of 3.3V, the second communication voltage cannot recognize it. Embodiments of the present invention perform communication voltage conversion based on the communication voltages of the two communication units, so that two communication units with any operating voltage can recognize each other's signals during communication. In other words, the embodiments of the present invention do not require the design of corresponding communication voltage conversion circuits based on the communication voltages of the two communication units. The embodiments of the present invention can achieve voltage conversion for communication units with any operating voltage, thereby reducing the design cost of the communication voltage conversion circuit.

[0054] See also Figure 1 , Figure 1 The functional block diagram of a communication voltage conversion circuit according to an embodiment of the present invention is shown. The communication voltage conversion circuit includes a receiving signal conversion circuit 10, which is used to convert a voltage signal sent by a first communication unit MCU-A into a communication voltage for a second communication unit MCU-B. The first communication unit MCU-A is the MCU of a wireless communication device, such as the MCU of a GPRS module; the second communication unit MCU-B is the MCU of an intelligent electrical appliance or electronic device. The receiving signal conversion circuit 10 includes a first switching circuit 11, a second switching circuit 12, a third switching circuit 13, and a first pull-up circuit 14. The input end of the first switching circuit 11 is connected to the first control terminal GPIO1 of the first communication unit MCU-A, the control end of the first switching circuit 11 is connected to the first power supply VDD1, and the output end of the first switching circuit 11 is connected to the first end of the first pull-up circuit 14. The first voltage VD1 of the first power supply VDD1 is the same as the communication voltage of the first communication unit MCU-A. The first switch circuit 11 is turned on or off according to a first control signal sent by the first control terminal GPIO1 of the first communication unit MCU-A. When the first switch circuit 11 is turned on, the voltage at the output terminal of the first switch circuit 11 is a first voltage VD1.

[0055] The input end of the second switch circuit 12 is connected to the first control end GPIO1 of the first communication unit MCU-A, the control end of the second switch circuit 12 is connected to the second power supply VDD2, and the output end of the second switch circuit 12 is connected to the first end of the first pull-up circuit 14; the second voltage VD2 of the second power supply VDD2 is the same as the communication voltage of the second communication unit MCU-B, and the second switch circuit 12 is turned on or off according to the first control signal; when the second switch circuit 12 is turned on, the voltage of the output end of the second switch circuit 12 is the second voltage VD2.

[0056] The input end of the third switch circuit 13 is connected to the first power supply VDD1, the control end of the third switch circuit 13 is connected to the signal transmitting end A-TXD of the first communication unit MCU-A, and the output end of the third switch circuit 13 is connected to the signal receiving end B-RXD of the second communication unit MCU-B. The third switch circuit 13 is turned on or off according to the voltage signal sent by the signal transmitting end of the first communication unit MCU-A. When the third switch circuit 13 is turned on, the output end of the third switch circuit 13 outputs the voltage signal sent by the signal transmitting end of the first communication unit MCU-A. That is, when the voltage signal sent by the signal transmitting end of the first communication unit MCU-A is VD1, the third switch circuit 13 outputs VD1; when the voltage signal sent by the signal transmitting end of the first communication unit MCU-A is 0, the third switch circuit 13 outputs 0.

[0057] A first end of the first pull-up circuit 14 is connected to the output end of the first switch circuit 11 and the output end of the second switch circuit 12 respectively, and a second end of the first pull-up circuit 14 is connected to the signal receiving end B-RXD of the second communication unit MCU-B.

[0058] When the communication voltage of the first communication unit MCU-A is different from the communication voltage of the second communication unit MCU-B, the first control signal is a high level, i.e., VD1, the first switch circuit 11 is turned off, the second switch circuit 12 is turned on, and the voltage at the first end of the first pull-up circuit 14 is the second voltage VD2; when the signal sending end of the first communication unit MCU-A sends a low voltage signal to the second communication unit MCU-B, the third switch circuit 13 is turned on, and the voltage signal received by the second communication unit MCU-B is a low voltage.

[0059] When the communication voltage of the first communication unit MCU-A is the same as the communication voltage of the second communication unit MCU-B, the first control signal is at a low level, i.e., 0, the first switch circuit 11 is turned on, the second switch circuit 12 is turned off, and the voltage at one end of the first pull-up circuit 14 connected to the output end of the first switch circuit 11 is the first voltage VD1; when the signal sending end of the first communication unit MCU-A sends a high voltage signal to the second communication unit MCU-B, the third switch circuit 13 is turned off, and the voltage signal received by the second communication unit MCU-B is the first voltage VD1; when the signal sending end of the first communication unit MCU-A sends a low voltage signal to the second communication unit MCU-B, the third switch circuit 13 is turned on, and the voltage signal received by the second communication unit MCU-B is a low voltage.

[0060] In some embodiments, see Figure 2 , Figure 2 FIG1 shows a schematic diagram of a communication voltage conversion circuit according to an embodiment of the present invention. Figure 2 In the embodiment, the first switching circuit 11 includes a first voltage-dividing resistor R19, a second voltage-dividing resistor R12, and a first PNP transistor Q12. The first voltage-dividing resistor R19 and the second voltage-dividing resistor R12 are connected in series between the first control terminal of the first communication unit MCU-A and the first power supply VDD1. The other end of the first voltage-dividing resistor R19 is connected to the first control terminal of the first communication unit MCU-A, and the other end of the second voltage-dividing resistor R12 is connected to the first power supply VDD1.

[0061] The base of the first PNP transistor Q12 is connected to the common end of the first voltage-dividing resistor R19 and the second voltage-dividing resistor R12, the emitter of the first PNP transistor Q12 is connected to the first power supply, the base of the first PNP transistor Q12 is connected to the common end of the first voltage-dividing resistor R19 and the second voltage-dividing resistor R12, and the collector of the first PNP transistor Q12 is connected to the first end of the first pull-up circuit 14.

[0062] When the first control signal is at a high level, i.e., VD1, the first PNP transistor Q12 is turned off; when the first control signal is at a low level, i.e., 0, the second voltage-dividing resistor R12 and the first voltage-dividing resistor R19 divide the first voltage VD1, so that the first PNP transistor Q12 is turned on, and the voltage of the collector of the first PNP transistor Q12 is the first voltage VD1.

[0063] In some embodiments, please refer to Figure 2The second switch circuit 12 includes: a third voltage-dividing resistor R11, a fourth voltage-dividing resistor R10, a second PNP transistor Q11, a first NPN transistor Q14 and a first current-limiting resistor R13. The third voltage-dividing resistor R11 and the fourth voltage-dividing resistor R10 are connected in series between the second power supply and the collector of the first NPN-type transistor Q14. The other end of the third voltage-dividing resistor R11 is connected to the second power supply, and the other end of the fourth voltage-dividing resistor R10 is connected to the collector of the first NPN-type transistor Q14. The base of the second PNP-type transistor Q11 is connected to the common end of the third voltage-dividing resistor R11 and the fourth voltage-dividing resistor R10, the emitter of the second PNP-type transistor Q11 is connected to the second power supply, and the collector of the second PNP-type transistor is connected to the first end of the first pull-up circuit 14. The base of the first NPN-type transistor Q14 is connected to the first control end of the first communication unit via the first current-limiting resistor, the collector of the first NPN-type transistor Q14 is connected to one end of the fourth voltage-dividing resistor R10, and the emitter of the first NPN-type transistor Q14 is grounded.

[0064] When the first control terminal of the first communication unit outputs a high level, the first NPN transistor Q14 is turned on, and the collector of the first NPN transistor Q14 outputs a low level, so that the second PNP transistor Q11 is turned on, and the voltage of the collector of the second PNP transistor Q11 is the second voltage; when the first control terminal GPIO1 of the first communication unit MCU-A outputs a low level, the first NPN transistor Q14 and the second PNP transistor Q11 are both turned off.

[0065] In some embodiments, please refer to Figure 2 The third switching circuit includes: a second NPN transistor Q13 and a second current-limiting resistor R15; the base of the second NPN transistor Q13 is connected to the first power supply VDD1 through the second current-limiting resistor R15, the emitter of the second NPN transistor Q13 is connected to the signal transmitting end of the first communication unit MCU-A, and the collector of the second NPN transistor Q13 is connected to the signal receiving end B-RXD of the second communication unit MCU-B.

[0066] When the first control terminal GPIO1 of the first communication unit MCU-A outputs a high level, the second NPN transistor Q13 is turned off; when the first control terminal GPIO1 of the first communication unit MCU-A outputs a low level, the second NPN transistor Q13 is turned on, and the collector of the second NPN transistor Q13 outputs a low level.

[0067] In some embodiments, please refer to Figure 2 , the first pull-up circuit 14 includes a first pull-up resistor R14.

[0068] Below Figure 2The working process of the circuit is explained.

[0069] When the communication voltage of the second communication unit MCU-B differs from the communication voltage of the first communication unit MCU-A, the first control terminal GPIO1 of the first communication unit MCU-A outputs a high-level first control signal, i.e., VD1. The first PNP transistor Q12 is turned off, the first NPN transistor Q14 is turned on, and the collector of the first NPN transistor Q14 outputs a low-level signal, turning on the second PNP transistor Q11. The potential of the first terminal of the first pull-up resistor R14 is equal to the emitter potential VD2 of the second PNP transistor Q11. In this case, if the signal transmitting terminal A-TXD of the first communication unit MCU-A transmits a high-level signal, i.e., VD1, the second NPN transistor Q13 is turned off, and the potential of the second terminal of the first pull-up resistor R14 is the same as the potential of the first terminal, i.e., VD2, causing the signal receiving terminal B-RXD of the second communication unit MCU-B to receive a high-level signal, i.e., VD2. If the signal transmitting terminal A-TXD of the first communication unit MCU-A sends a low-level signal, the second NPN transistor Q13 is turned on, the potential of the second end of the first pull-up resistor R14 is low, and the first pull-up resistor R14 consumes the voltage VD2 of the first end, so that the signal receiving terminal B-RXD of the second communication unit MCU-B receives a low-level signal.

[0070] When the communication voltage of the second communication unit MCU-B is the same as the communication voltage of the first communication unit MCU-A, the first control terminal GPIO1 of the first communication unit MCU-A outputs a low-level first control signal. The first PNP transistor Q12 is turned on, the first NPN transistor Q14 is turned off, and the base of the second PNP transistor Q11 has no current. The second PNP transistor Q11 is turned off, and the first end potential of the first pull-up resistor R14 is equal to the emitter potential VD1 of the first PNP transistor Q12. In this case, if the signal transmitting terminal A-TXD of the first communication unit MCU-A sends a high-level signal, i.e., VD1, the second NPN transistor Q13 is turned off, and the second end potential of the first pull-up resistor R14 is equal to the first end potential, i.e., VD1, thereby causing the signal receiving terminal B-RXD of the second communication unit MCU-B to receive a high-level signal, i.e., VD1. If the signal transmitting terminal A-TXD of the first communication unit MCU-A sends a low-level signal, the second NPN transistor Q13 is turned on, the potential of the second end of the first pull-up resistor R14 is low, and the first pull-up resistor R14 consumes the voltage VD1 of the first end, so that the signal receiving terminal B-RXD of the second communication unit MCU-B receives a low-level signal.

[0071] Before sending the first control signal, the first communication unit MCU-A automatically identifies the communication level of the second communication unit MCU-B. The specific identification method is described in the following embodiment. Please refer to the specific description of the embodiment below and will not be repeated here.

[0072] Through the embodiment of the present invention, no matter what the communication voltage of the second communication unit MCU-B is, the second communication unit MCU-B can receive a voltage that matches its communication voltage. Compared with the prior art in which corresponding communication voltage conversion circuits are specially designed for second communication units MCU-B with different communication voltages, the embodiment of the present invention can be applicable to second communication units MCU-B with any communication voltage, thereby saving the design cost of the communication voltage conversion circuit.

[0073] Figure 3 FIG. 4 shows a functional block diagram of a communication voltage conversion circuit according to another embodiment of the present invention. Figure 3 As shown, the communication voltage conversion circuit in the embodiment of the present invention also includes a transmission signal conversion circuit 20. The transmission signal conversion circuit 20 is used to convert the voltage signal sent by the second communication unit MCU-B into the communication voltage of the first communication unit MCU-A; the transmission signal conversion circuit 20 includes a fourth switch circuit 21, a fifth switch circuit 22, a sixth switch circuit 23, and a second pull-up circuit 24. The input end of the fourth switch circuit 21 is connected to the second control terminal GPIO2 of the first communication unit MCU-A, the control end of the fourth switch circuit 21 is connected to the first power supply VDD1, and the output end of the fourth switch circuit 21 is connected to the first end of the second pull-up circuit 24; the fourth switch circuit 21 is turned on or off according to the second control signal sent from the second control terminal GPIO2 of the first communication unit MCU-A; when the fourth switch circuit 21 is turned on, the voltage at the output end of the fourth switch circuit 21 is the first voltage VD1.

[0074] The input end of the fifth switch circuit 22 is connected to the second control end GPIO2 of the first communication unit MCU-A, the control end of the fifth switch circuit 22 is connected to the first power supply VDD1, and the output end of the fifth switch circuit 22 is connected to the first end of the second pull-up circuit 24. The fifth switch circuit 22 is turned on or off according to the second control signal; when the fifth switch circuit 22 is turned on, the voltage at the output end of the fifth switch circuit 22 is the first voltage VD1.

[0075] The input end of the sixth switch circuit 23 is connected to the second power supply VDD2, the control end of the sixth switch circuit 23 is connected to the signal sending end B-TXD of the second communication unit MCU-B, and the output end of the sixth switch circuit 23 is connected to the signal receiving end A-RXD of the first communication unit MCU-A; the sixth switch circuit 23 is turned on or off according to the voltage signal sent by the signal sending end of the second communication unit MCU-B; when the sixth switch circuit 23 is turned on, the output end of the sixth switch circuit 23 outputs the voltage signal sent by the signal sending end of the second communication unit MCU-B.

[0076] A first end of the second pull-up circuit 24 is connected to the output end of the fourth switch circuit 21 and the output end of the fifth switch circuit 22, respectively. A second end of the second pull-up circuit 24 is connected to the signal receiving end A-RXD of the first communication unit MCU-A.

[0077] When the communication voltage of the first communication unit MCU-A is different from the communication voltage of the second communication unit MCU-B, the second control signal is at a high level, the fourth switch circuit 21 is turned off, the fifth switch circuit 22 is turned on, and the voltage at the first end of the second pull-up circuit 24 is the first voltage; when the signal sending end B-TXD of the second communication unit MCU-B sends a high voltage signal to the first communication unit MCU-A, the sixth switch circuit 23 is turned off, and the voltage signal received by the first communication unit 21 is the first voltage VD1; when the signal sending end B-TXD of the second communication unit MCU-B sends a low voltage signal to the first communication unit MCU-A, the sixth switch circuit 23 is turned on, and the voltage signal received by the first communication unit 21 is a low voltage.

[0078] In an embodiment of the present invention, when the communication voltage of the first communication unit MCU-A is different from the communication voltage of the second communication unit MCU-B, the first control signal and the second control signal are both at a high level, and when the communication voltage of the first communication unit MCU-A is the same as the communication voltage of the second communication unit MCU-B, the first control signal and the second control signal are both at a low level. Therefore, the first control terminal GPIO1 and the second control terminal GPIO2 of the first communication unit MCU-A can be the same terminal. In this way, only one control signal needs to be sent to simultaneously control the receiving signal conversion circuit 10 and the transmitting signal conversion circuit 20, thereby reducing the control cost and the port development cost of the first communication unit MCU-A.

[0079] Figure 3 The transmission signal conversion circuit 20 in the communication voltage conversion circuit shown corresponds to the reception signal conversion circuit 10, and the implementation of each specific circuit in the transmission signal conversion circuit 20 corresponds to the implementation of each specific circuit in the reception signal conversion circuit 10. That is, the fourth switch circuit 21 in the transmission signal conversion circuit 20 can be implemented as Figure 2 The first switch circuit 11 in the receiving signal conversion circuit 10; the fifth switch circuit 22 in the sending signal conversion circuit 20 can be implemented as Figure 2 The second switch circuit 12 in the receiving signal conversion circuit 10; the sixth switch circuit 23 in the sending signal conversion circuit 20 can be implemented as Figure 2 The third switch circuit 13 in the receiving signal conversion circuit 10. In this implementation, the schematic diagram of the corresponding communication voltage conversion circuit is as follows Figure 4 As shown, Figure 4 The operation process of the fourth switch circuit 21, the fifth switch circuit 22, the sixth switch circuit 23 and the second pull-up circuit 24 is the same as the operation process of the first switch circuit 11, the second switch circuit 12, the third switch circuit 13 and the first pull-up circuit 14. Figure 2 The corresponding instructions are not repeated here.

[0080] In some embodiments, the communication voltage of the second communication unit MCU-B is higher than the communication voltage of the first communication unit MCU-A, and the communication voltages of different first communication units MCU-A are the same. In these embodiments, the schematic diagram of the communication voltage conversion circuit is as follows: Figure 5 As shown. Figure 5 In the example, the transmitting signal conversion circuit 20 includes: a fifth voltage-dividing resistor R16, a sixth voltage-dividing resistor R17, a third NPN transistor Q15, and a second current-limiting resistor R18. The fifth voltage-dividing resistor R16 and the sixth voltage-dividing resistor R17 are connected in series between the signal transmitting terminal B-TXD of the second communication unit MCU-B and the collector of the third NPN transistor Q15. The other end of the fifth voltage-dividing resistor R16 is connected to the signal transmitting terminal B-TXD of the second communication unit MCU-B. The sixth voltage-dividing resistor R17 is connected to the collector of the third NPN transistor Q15. The emitter of the third NPN transistor Q15 is grounded, and the base of the third NPN transistor Q15 is connected to the second control port GPIO2 of the first communication unit MCU-A via the second current-limiting resistor R18. The third NPN transistor Q15 is turned on or off according to the second control signal sent from the second control port GPIO2 of the first communication unit MCU-A.

[0081] When the communication voltage of the first communication unit MCU-A is lower than the communication voltage of the second communication unit MCU-B, the second control signal is at a high level, the third NPN transistor Q15 is turned on, the sixth voltage-dividing resistor R17 and the fifth voltage-dividing resistor R16 divide the voltage signal sent by the second communication unit MCU-B to obtain the voltage signal of the first communication unit MCU-A, and send it to the signal receiving end A-RXD of the first communication unit MCU-A.

[0082] When the communication voltage of the first communication unit MCU-A is the same as the communication voltage of the second communication unit MCU-B, the second control signal is low, the third NPN transistor Q15 is turned off, and the second communication unit MCU-B sends a voltage signal to the first communication unit MCU-A through the fifth voltage divider resistor R16.

[0083] The transmission signal conversion circuit 20 provided by the embodiment of the present invention is compared with Figure 4 The transmission signal conversion circuit 20 reduces the number of components and lowers the design cost of the transmission signal conversion circuit 20.

[0084] In some embodiments, please refer to Figure 5 The transmission signal conversion circuit 20 also includes a protection diode D11; the anode of the protection diode D11 is connected to the common end of the fifth voltage-dividing resistor R16 and the sixth voltage-dividing resistor R17, and the cathode of the protection diode D11 is connected to the first power supply VDD1. When the voltage of the sixth voltage-dividing resistor R17 is greater than the first voltage VD1, the protection diode D11 conducts, and the voltage at the signal receiving terminal A-RXD of the first communication unit MCU-A is less than the sum of the first voltage VD1 and the voltage drop of the protection diode D11. For example, if the voltage drop of the protection diode is 0.5V, the protection diode can limit the voltage at the signal receiving terminal A-RXD of the first communication unit MCU-A to within VD1 + 0.5V, thereby preventing damage to the first communication unit MCU-A.

[0085] Figure 6 FIG. 1 shows a schematic structural diagram of a communication device according to an embodiment of the present invention. Figure 6 As shown, the communication device includes: a first communication unit MCU-A and a communication voltage conversion circuit 100. Among them, the first communication unit MCU-A includes a first control terminal GPIO1, a second control terminal GPIO2, a signal sending terminal A-TXD and a signal receiving terminal A-RXD. The first control terminal GPIO1 and the second control terminal GPIO2 can be the same terminal or different terminals, and the embodiment of the present invention is not limited to this. The first control terminal GPIO1 and the second control terminal GPIO2 send a first control signal and a second control signal to the communication voltage conversion circuit 100. The voltage conversion circuit 100 in the embodiment of the present invention is the communication voltage conversion circuit in any of the above-mentioned embodiments. For the connection method between the first control terminal GPIO1 and the second control terminal GPIO2 and the communication voltage conversion circuit 100, please refer to the specific description of the above-mentioned embodiment.

[0086] The communication device in the embodiment of the present invention can be implemented as any communication device, for example, a GPRS module. When the communication device is a GPRS module, the GPRS module includes a GPRS module and a communication voltage conversion circuit, and the first communication unit is the MCU of the GPRS module.

[0087] The communication device according to the embodiment of the present invention can realize communication with the second communication unit MCU-B of any voltage, thereby reducing the development cost of the communication device.

[0088] Figure 7 A communication voltage identification method according to an embodiment of the present invention is shown, which is applied to a first communication unit. The method includes the following steps:

[0089] Step 701: Send a low-level first control signal and a low-level second control signal to the receiving signal conversion circuit and the transmitting signal conversion circuit respectively, and send test data to the second communication unit to obtain a test result.

[0090] In this step, the receiving signal conversion circuit and the transmitting signal conversion circuit are the receiving signal conversion circuit and the transmitting signal conversion circuit in any one of the above-mentioned communication voltage conversion circuit embodiments.

[0091] Step 702: Determine whether the response data sent by the second communication unit is received, if yes, execute step 703, if not, execute step 704.

[0092] In this step, the second communication unit returns response data to the first communication unit only when it receives test data sent by the first communication unit. When a low level is sent to the receiving signal conversion circuit, the first switch circuit in the receiving signal conversion circuit is turned on and the second switch circuit is turned off, and the test data sent to the second communication unit does not undergo voltage conversion. Similarly, when a low level is sent to the transmitting signal conversion circuit, the transmitting signal conversion circuit does not perform level conversion. If response data is received from the second communication unit, it means that the second communication unit has received the test data sent by the first communication unit without performing voltage conversion, that is, the communication level of the second communication unit is the same as the communication level of the first communication unit. Otherwise, the communication level of the second communication unit is different from the communication level of the first communication unit.

[0093] Step 703 : Determine that the test result shows that the communication voltage of the second communication unit is the same as the communication voltage of the first communication unit.

[0094] In this step, if the response data sent by the second communication unit is received, it is determined that the communication voltage of the second communication unit is the same as the communication voltage of the first communication unit.

[0095] Step 704 : Determine that the test result is that the communication voltage of the second communication unit is different from the communication voltage of the first communication unit.

[0096] In this step, if the response data sent by the second communication unit is not received, it is determined that the communication voltage of the second communication unit is different from the communication voltage of the first communication unit.

[0097] Step 705: Send a first control signal and a second control signal to the receiving signal conversion circuit and the transmitting signal conversion circuit respectively according to the test results.

[0098] In this step, after determining the communication voltage of the second communication unit, a first control signal and a second control signal are sent. If the communication voltage of the second communication unit is different from the communication voltage of the first communication unit, the first control signal and the second control signal are both high; if the communication voltage of the second communication unit is the same as the communication voltage of the first communication unit, the first control signal and the second control signal are both low.

[0099] The embodiment of the present invention can test whether the communication voltage of the second communication unit is consistent with the communication voltage of the first communication unit, so as to send different first control signals and second control signals according to the test results to achieve reliable communication between the first communication unit and the second communication unit.

[0100] Figure 8 FIG. 1 shows a schematic diagram of the structure of a communication unit according to an embodiment of the present invention. Figure 8 As shown, the communication unit includes a processor 402 , a communications interface 404 , a memory 406 , and a communication bus 408 .

[0101] Processor 402, communication interface 404, and memory 406 communicate with each other via communication bus 408. Communication interface 404 is used to communicate with other devices, such as clients or other server network elements. Processor 402 is used to execute program 410, which may specifically perform the steps described in the aforementioned embodiment of the method for identifying communication voltage.

[0102] Specifically, the program 410 may include program code including computer-executable instructions.

[0103] Processor 402 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention. The one or more processors included in the communication unit may be processors of the same type, such as one or more CPUs, or processors of different types, such as one or more CPUs and one or more ASICs.

[0104] The memory 406 is used to store the program 410. The memory 406 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0105] Program 410 can be specifically called by processor 402 to enable the communication unit to execute Figure 7 Steps 701 to 705 in .

[0106] It should be noted that, unless otherwise specified, technical terms or scientific terms used in the embodiments of the present invention should have the common meanings understood by those skilled in the art to which the embodiments of the present invention belong.

[0107] In the description of the present embodiment, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present invention.

[0108] In addition, the technical terms "first," "second," etc. are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly indicate the number of the technical features indicated. In the description of the embodiments of the present invention, the meaning of "plurality" is more than two, unless otherwise specifically defined.

[0109] In the description of the present embodiment, unless otherwise specified or limited, technical terms such as "installed," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on specific circumstances.

[0110] In the description of this embodiment, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A communication voltage conversion circuit, characterized in that: The circuit includes a receiving signal conversion circuit; the receiving signal conversion circuit is used to convert the voltage signal sent by the first communication unit into a communication voltage of the second communication unit; the receiving signal conversion circuit includes: a first switch circuit, a second switch circuit, a third switch circuit and a first pull-up circuit; The input end of the first switch circuit is connected to the first control end of the first communication unit, the control end of the first switch circuit is connected to a first power source, and the output end of the first switch circuit is connected to the first end of the first pull-up circuit; the first voltage of the first power source is the same as the communication voltage of the first communication unit; the first switch circuit is turned on or off according to a first control signal sent by the first control end of the first communication unit; when the first switch circuit is turned on, the voltage of the output end of the first switch circuit is the first voltage; An input end of the second switch circuit is connected to the first control end of the first communication unit, a control end of the second switch circuit is connected to a second power supply, and an output end of the second switch circuit is connected to the first end of the first pull-up circuit; a second voltage of the second power supply is the same as a communication voltage of the second communication unit, and the second switch circuit is turned on or off according to the first control signal; when the second switch circuit is turned on, a voltage at the output end of the second switch circuit is the second voltage; The input end of the third switch circuit is connected to the first power supply, the control end of the third switch circuit is connected to the signal sending end of the first communication unit, and the output end of the third switch circuit is connected to the signal receiving end of the second communication unit. The third switch circuit is turned on or off according to the voltage signal sent by the signal sending end of the first communication unit. When the third switch circuit is turned on, the output end of the third switch circuit outputs the voltage signal sent by the signal sending end of the first communication unit. The third switch circuit includes: a second NPN transistor and a second current-limiting resistor. The base of the second NPN transistor is connected to the first power supply through the second current-limiting resistor, the emitter of the second NPN transistor is connected to the signal sending end of the first communication unit, and the collector of the second NPN transistor is connected to the signal receiving end of the second communication unit. When the first control end of the first communication unit outputs a high level, the second NPN transistor is turned off. When the first control end of the first communication unit outputs a low level, the second NPN transistor is turned on, and the collector of the second NPN transistor outputs a low level. A first end of the first pull-up circuit is connected to the output end of the first switch circuit and the output end of the second switch circuit respectively, and a second end of the first pull-up circuit is connected to the signal receiving end of the second communication unit; When the communication voltage of the first communication unit is different from the communication voltage of the second communication unit, the first control signal is at a high level, the first switch circuit is turned off, the second switch circuit is turned on, and the voltage at the first end of the first pull-up circuit is the second voltage; when the signal sending end of the first communication unit sends a high voltage signal to the second communication unit, the third switch circuit is turned off, and the voltage signal received by the second communication unit is the second voltage; when the signal sending end of the first communication unit sends a low voltage signal to the second communication unit, the third switch circuit is turned on, and the voltage signal received by the second communication unit is a low voltage.

2. The circuit according to claim 1, wherein: The first switch circuit includes: a first voltage-dividing resistor, a second voltage-dividing resistor and a first PNP transistor; The first voltage-dividing resistor and the second voltage-dividing resistor are connected in series between the first control terminal of the first communication unit and the first power supply, the other end of the first voltage-dividing resistor is connected to the first control terminal of the first communication unit, and the other end of the second voltage-dividing resistor is connected to the first power supply; The base of the first PNP transistor is connected to the common end of the first voltage-dividing resistor and the second voltage-dividing resistor, the emitter of the first PNP transistor is connected to the first power supply, and the collector of the first PNP transistor is connected to the first end of the first pull-up circuit; When the first control signal is at a high level, the first PNP transistor is turned off; when the first control signal is at a low level, the second voltage-dividing resistor and the first voltage-dividing resistor divide the first voltage, so that the first PNP transistor is turned on, and the voltage of the collector of the first PNP transistor is the first voltage.

3. The circuit according to claim 1, wherein: The second switch circuit includes: a third voltage-dividing resistor, a fourth voltage-dividing resistor, a first NPN transistor, a second PNP transistor and a first current-limiting resistor; The third voltage-dividing resistor and the fourth voltage-dividing resistor are connected in series between the second power supply and the collector of the first NPN transistor, the other end of the third voltage-dividing resistor is connected to the second power supply, and the other end of the fourth voltage-dividing resistor is connected to the collector of the first NPN transistor; The base of the first NPN transistor is connected to the first control terminal of the first communication unit through the first current limiting resistor, the collector of the first NPN transistor is connected to one end of the fourth voltage dividing resistor, and the emitter of the first NPN transistor is grounded; The base of the second PNP transistor is connected to the common end of the third voltage-dividing resistor and the fourth voltage-dividing resistor, the emitter of the second PNP transistor is connected to the second power supply, and the collector of the second PNP transistor is connected to the first end of the first pull-up circuit; When the first control end of the first communication unit outputs a high level, the first NPN transistor is turned on, and the collector of the first NPN transistor outputs a low level, so that the second PNP transistor is turned on, and the voltage of the collector of the second PNP transistor is the second voltage; when the first control end of the first communication unit outputs a low level, both the first NPN transistor and the second PNP transistor are turned off.

4. The circuit according to claim 1, wherein: The circuit further includes a sending signal conversion circuit, the sending signal conversion circuit being used to convert the voltage signal sent by the second communication unit into a communication voltage of the first communication unit; the sending signal conversion circuit includes a fourth switch circuit, a fifth switch circuit, a sixth switch circuit and a second pull-up circuit; An input end of the fourth switch circuit is connected to the second control end of the first communication unit, a control end of the fourth switch circuit is connected to the first power supply, and an output end of the fourth switch circuit is connected to the first end of the second pull-up circuit; the fourth switch circuit is turned on or off according to a second control signal sent by the second control end of the first communication unit; when the fourth switch circuit is turned on, a voltage at the output end of the fourth switch circuit is the first voltage; An input end of the fifth switch circuit is connected to the second control end of the first communication unit, a control end of the fifth switch circuit is connected to the first power supply, an output end of the fifth switch circuit is connected to the first end of the second pull-up circuit, and the fifth switch circuit is turned on or off according to the second control signal; when the fifth switch circuit is turned on, a voltage at the output end of the fifth switch circuit is the first voltage; The input end of the sixth switch circuit is connected to the second power supply, the control end of the sixth switch circuit is connected to the signal sending end of the second communication unit, and the output end of the sixth switch circuit is connected to the signal receiving end of the first communication unit; the sixth switch circuit is turned on or off according to the voltage signal sent by the signal sending end of the second communication unit; when the sixth switch circuit is turned on, the output end of the sixth switch circuit outputs the voltage signal sent by the signal sending end of the second communication unit; The first end of the second pull-up circuit is connected to the output end of the fourth switch circuit and the output end of the fifth switch circuit respectively, and the second end of the second pull-up circuit is connected to the signal receiving end of the first communication unit; When the communication voltage of the first communication unit is different from the communication voltage of the second communication unit, the second control signal is at a high level, the fourth switch circuit is turned off, the fifth switch circuit is turned on, and the voltage at the first end of the second pull-up circuit is the first voltage; when the signal sending end of the second communication unit sends a high voltage signal to the first communication unit, the sixth switch circuit is turned off, and the voltage signal received by the first communication unit is the first voltage; when the signal sending end of the second communication unit sends a low voltage signal to the first communication unit, the sixth switch circuit is turned on, and the voltage signal received by the first communication unit is a low voltage.

5. The circuit according to claim 1, wherein: The circuit further includes a sending signal conversion circuit, which is used to convert the voltage signal sent by the second communication unit into a communication voltage of the first communication unit; the sending signal conversion circuit includes: a fifth voltage dividing resistor, a sixth voltage dividing resistor, a third NPN transistor and a second current limiting resistor; The fifth voltage-dividing resistor and the sixth voltage-dividing resistor are connected in series between the signal transmitting end of the second communication unit and the collector of the third NPN-type transistor, the other end of the fifth voltage-dividing resistor is connected to the signal transmitting end of the second communication unit, the sixth voltage-dividing resistor is connected to the collector of the third NPN-type transistor, the emitter of the third NPN-type transistor is grounded, and the base of the third NPN-type transistor is connected to the second control port of the first communication unit via the second current-limiting resistor; the third NPN-type transistor is turned on or off according to the second control signal sent by the second control port of the first communication unit; When the communication voltage of the first communication unit is lower than the communication voltage of the second communication unit, the second control signal is at a high level, the third NPN transistor is turned on, the sixth voltage-dividing resistor and the fifth voltage-dividing resistor divide the voltage signal sent by the second communication unit to obtain the voltage signal of the first communication unit, and send it to the signal receiving end of the first communication unit; When the communication voltage of the first communication unit is the same as the communication voltage of the second communication unit, the second control signal is at a low level, the third NPN transistor is turned off, and the second communication unit sends a voltage signal to the first communication unit through the fifth voltage-dividing resistor.

6. The circuit according to claim 5, characterized in that The sending signal conversion circuit also includes a protection diode; the positive electrode of the protection diode is connected to the common end of the fifth voltage-dividing resistor and the sixth voltage-dividing resistor, and the negative electrode of the protection diode is connected to the first power supply; when the voltage of the sixth voltage-dividing resistor is greater than the first voltage, the protection diode is turned on, so that the voltage at the signal receiving end of the first communication unit is less than the sum of the first voltage and the voltage drop of the protection diode.

7. A communication device, characterized in that: The communication device includes: a first communication unit and a communication voltage conversion circuit; the first communication unit includes a first control end, a second control end, a signal sending end and a signal receiving end; the communication voltage conversion circuit is the communication voltage conversion circuit as described in any one of claims 1-6.

8. A method for identifying a communication voltage, applied to a first communication unit, characterized in that: The method comprises: Sending a low-level first control signal and a low-level second control signal to the receiving signal conversion circuit and the transmitting signal conversion circuit respectively, and sending test data to the second communication unit to obtain a test result; If the response data sent by the second communication unit is received, determining that the test result is that the communication voltage of the second communication unit is the same as the communication voltage of the first communication unit; otherwise, determining that the test result is that the communication voltage of the second communication unit is different from the communication voltage of the first communication unit; sending a first control signal and a second control signal to the receiving signal conversion circuit and the transmitting signal conversion circuit respectively according to the test result; The receiving signal conversion circuit is the receiving signal conversion circuit in the communication voltage conversion circuit according to any one of claims 1 to 5; the sending signal conversion circuit is the sending signal conversion circuit in the communication voltage conversion circuit according to claim 4 or 5.

9. A communication unit, characterized in that: The communication unit includes: a processor, a memory, a communication interface and a communication bus, and the processor, the memory and the communication interface communicate with each other through the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute operations corresponding to the communication voltage identification method according to claim 8.

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